Within the NPS shrubs overall height and/or spread at the time of sale is significant, additionally qualified by reference to the number of branches (or breaks) which is to be expected for the plant of that size. Shrubs vary from compact, slow-growing species, to low forms, through medium-size types to vigorous, fast-growing species and it is important to specify appropriately for each type.
The use of height and/or spread dimensions depends on the characteristics of the species and the dimensions which are most appropriate at the time of sale. The following tables give information about the general grades for shrubs in cultivation.
- Container-grown Shrubs: Overall Height and Spread
- Bare-root Shrubs
- Bare-rootballed Shrubs
- Rhododendrons and Azaleas:
- Cell-grown Shrubs
All forms of shrubs are supplied in containers. The following are the typical overall height grades used for the supply of container-grown shrubs. The actual grade is determined by cultural conditions and the characteristics of the species/cv. Typically, the height is specified except for compact/low growing shrubs or ground covers where spread is specified.
|Overall Height in cm|
For Specimen shrubs both height and spread may be specified.
Typical overall spread grades
Typically the spread grade is specified for compact/low growing shrubs or ground covers. The following are the typical overall spread grades used for the supply of container-grown shrubs. The actual grade is determined by the cultural conditions of the plant and the characteristics of the species/cv.
|Overall Spread in cm|
|Compact, low, medium and vigorous species/cvs (height in cm)|
|Low/compact: e.g. Cotoneaster ‘Coral Beauty’; Genista lydia; Potentilla ‘Elizabeth’ (height in cm)|
|Medium: e.g. Berberis thunbergii, Cytisus scoparius; Escallonia ‘Slieve Donard’ (height in cm)|
*>250cm = 50 cm increments; >400cm=100cm increments.
|Vigorous: e.g.Cotoneaster ‘Cornubia’; Elaeagnus x ebbingei; Hippophae rhamnoides (height/spread in cm)|
|Ground cover: Ceanothus thyrsiflorus repens; Cotoneaster dammeri; Euonymus fortunei cvs.(spread in cm)|
Specimen shrubs must have both height and spread.
For genus Rhododendron the following grades apply:
|Low/compact and medium (height or spread in cm)|
|Vigorous (height or spread in cm)|
For deciduous Azaleas, the following grades apply:
|Deciduous Azaleas (height in cm)|
|Japanese Azaleas (height in cm)|
Cells are used for the production of seed-raised trees and shrubs. The following height grades are used. In addition, it is important to specify the CELL VOLUME and the minimum ROOT COLLAR DIAMETER in specifying cell grown shrubs.
|Overall height (cm)||Volume||Root collar dia.|